This invention relates to indicating devices for displaying liquid level condition within a tank or other container, and more particularly to a system and method for optically determining and remotely signaling a low liquid level condition within a tank.
Conventional forklifts typically include a vehicle frame, a mast attached to the front end of the vehicle frame, a fork carriage adapted for elevational movement along the mast to raise and lower loads, and a counterweight located at the rear end of the vehicle frame for retaining balance of the forklift as heavyweight loads are lifted. An engine is typically mounted at the center of the vehicle frame and usually is covered with a hood. A driver's seat is typically fixedly secured to the hood and surrounded by an overhead guard which defines a cabin. Many such forklifts are powered by liquid propane and therefore include a liquid propane tank that is removably mounted for the purpose of refueling on a support structure of the counterweight. In order to prevent forklift down time or the chance of fuel outage at a location remote from the replacement tank, the propane tank is often replaced before it is completely empty. Since some tanks do not have a fuel gauge, a significant amount of cost can be incurred since useful amounts of propane may be left in the tank upon replacement. Even if a fuel sight gauge is provided, the dial indicator is not readily viewable by an operator.
In order to overcome this disadvantage, remote ready gauges have been provided. Such gauges employ a magnetically driven dial for physically viewing the liquid level as well as a magnetic flux field sensor mounted on the dial for monitoring a position of the dial and generating an electric signal indicative of liquid level within the tank. Such a device is disclosed in U.S. Pat. No. 6,564,632 issued to Herbert G. Ross, Jr. on May 20, 2003. Although this device can provide the operator a means for remotely viewing the liquid level condition within the tank without leaving the operating position, it can become damaged if precautions are not observed. For example, if the magnetic flux field sensor is not removed from the gauge head before the tank is exchanged, the sensor, transmission cable and/or dial can become damaged and thus prevent transmission of the liquid level condition to the remote position.
Moreover, although it is convenient for an operator to view the liquid level condition of the tank from the operating position, the operator is preoccupied with the task at hand which often requires precise maneuvering of heavy overhead loads between narrowly spaced rows of stacked inventory items. Consequently, little attention may be paid to the remote indicator until the forklift runs out of fuel, resulting in undesired downtime for replacing the tank from an inconvenient location.
It would therefore be desirous to eliminate problems associated with prior art remote indicating devices while providing a signal to the operator when the tank reaches a predetermined low level condition.